- class Solution {
- public String longestPalindrome(String s) {
- if (s == null || s.length() <1) return "";
- int start = 0;
- int end = 0;
- for (int i = 0; i <s.length(); i++) {
- int len1 = expandFromMiddle(s, i, i);
- int len2 = expandFromMiddle(s, i, i + 1);
- int len = Math.max(len1, len2);
- if (len> end - start) {
- start = i - ((len - 1) / 2);
- end = i + (len / 2);
- }
- }
- return s.substring(start, end + 1);
- }
- private int expandFromMiddle(String s, int left, int right) {
- if (s == null || left> right) return 0;
- while (left>= 0 && right < s.length() && s.charAt(left) == s.charAt(right)) {
- left--;
- right++;
- }
- return right - left - 1;
- }
- }
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